Thermal imaging cameras are used in a variety of situations. For example, thermal imaging cameras are often used during maintenance inspections to thermally inspect equipment. Example equipment may include rotating machinery, electrical panels, or rows of circuit breakers, among other types of equipment. Thermal inspections can detect equipment hot spots such as overheating machinery or electrical components, helping to ensure timely repair or replacement of the overheating equipment before a more significant problem develops.
The dynamic range of a thermal image or a thermal imaging camera refers to the range of temperatures of a target scene that can be imaged by the camera at any one time. A large dynamic range corresponds to a large range of temperatures visible in a thermal image. In contrast, a small dynamic range implies that there is a relatively smaller range of temperatures observable within the scene.
Large and small dynamic ranges may be properties of thermal imaging cameras, or may be byproducts of parameters of the cameras. For example, a camera with an adjustable gain setting has a similarly adjustable dynamic range. As the gain of the camera is increased, the dynamic range generally decreases; similarly to the way in which zooming in on an image decreases the observable spatial range on a fixed display. The dynamic range in an image corresponds also to the amount of relative noise in an image. A larger dynamic range in an image will result in a lower signal-to-noise ratio as compared to an image of the same scene but a smaller dynamic range. On the other hand, a smaller dynamic range can result in saturation in an image if components of the thermal scene are present whose temperatures lie outside of the dynamic range.
Thus, a balance point is desired, wherein the dynamic range of thermal image is large enough so that the image does not saturate, but is kept small enough so as to minimize the amount of noise present in the image. This becomes more difficult as larger thermal ranges are demanded. Thermal scenes with a wide range of temperatures require a large dynamic range to be able to observe each temperature. However, the increase in noise can make it difficult to resolve portions of the image.
Previous systems have attempted to address this tradeoff by providing multiple thermal images, each image comprising neighboring or partly overlapping dynamic ranges. The system then scans the entirety of each image and selects portions from each image within its prescribed dynamic range to implement into a final image with an effective dynamic range spanning that of the set of images.